This invention is directed to a method for the manufacture of N-substituted-oxazolidines. More specifically, the invention is directed to a method for their manufacture using substituted imines. Oxazolidines are useful as intermediates in the production of monoalkoxylated amines.
Processes for the manufacture of compounds similar to the oxazolidine of the present reaction from imines and substituted oxiranes are disclosed in Chemical Abstracts, Vol. 98, 4493j, an abstract of the article in Izvestiya Akademii Nauk SSSR Seriya Kimicheskaya, v. 8, pp. 1872-1876 (1982), entitled "[2+3] Cycloadditions of Oxiranes and Thiiranes." The authors, A. V. Fokin, A. F. Kolomiets, G. F. Illin, and T. J. Fedyushina, disclose that oxiranes undergo cycloaddition with RSO.sub.2 N:CR.sub.1 CF.sub.3 in the manner as shown in the following example: ##STR3## As may be seen by the product's formula, the substitution at the nitrogen atom of the oxazolidine includes an --SO.sub.2 -group. This reference teaches that the imine of hexafluoroacetone (no substituted --SO.sub.2 -- on the nitrogen) will not react with ethylene oxide under mild conditions.
U.S. Pat. No. 3,743,626 to Emmons (Emmons I) teaches preparation of oxazolidine intermediates by several different methods. In one method, a Michael addition product, such as that formed by reacting a primary alkanolamine with an ester of .alpha.,.beta.-ethylenically unsaturated carboxylic acid, is reacted with an appropriate carbonyl compound to produce a monofunctional oxazolidine having ester functionality. In another method an aldehyde is reacted with ethanolamine to form a reaction mixture containing oxazolidine. The oxazolidine having ester functionality as above prepared is then transesterified by reaction with an unsaturated polyol, such as polyoxyalkylene polyol prepared by the addition of ethylene oxide to water.
U.S. Pat. No. 3,897,362 to McCoy describes the preparation of alkoxylated Schiff bases. First, a monoethoxylated Schiff base is made e.g., from aminoethanol and ketone. Ethylene oxide is then catalytically reacted with the Schiff base to form linear polyethoxylates, i.e. the ethylenoxide adds to the hydroxyl group.
U.S. Pat. No. 3,912,691, Emmons (Emmons II), discloses at column 6, lines 16-41, the cleaving with water (hydrolysis) of an oxazolidine to form a monoethoxylated amine. Trace amounts of moisture in the atmosphere are sufficient to initiate this hydrolysis. Emmons II incorporates Emmons I by reference in describing the preparation of the oxazolidines.
Other prior art discloses the manufacture of N-alkyl monoethoxylated amines by the direct addition of an N-alkyl amine to ethylene oxide. However, this process results in a conversion to the desired product of only about 25%, with 50% being converted to a diethoxylated amine and 25% remaining as unreacted amine. In addition to these low yields, a further problem arises in that the resulting mixture cannot be readily distilled or otherwise separated into its component parts.
Another prior art method comprises blending a primary amine with chlorohydrin to form an N-alkyl monoethoxylated ammonium chloride, which is thereafter neutralized with sodium hydroxide to form the N-alkyl monoethoxylated amine. The high cost of chlorohydrin renders this method somewhat undesirable.
Long chain N-alkyl monoethoxylated amines may also be manufactured by adding long-chain N-alkyl aldehydes to a alkanolamine, but the high cost of such aldehydes renders such a process commercially uneconomical.